The afferent neural response to electrotactile stimuli: preliminary results.

We recorded action potentials from three RA fibers innervating primate fingerpad, while applying electrotactile (electrocutaneous) stimulation. Negative pulses required 1.3-1.5 times more current than positive ones for entrainment. The strength-duration time constant was approximately 151 micros. Suprathreshold sinusoidal vibration synchronized to 30-Hz electrotactile pulses changed the electrotactile entrainment current slightly, indicating a possible electrical-mechanical transduction interaction.     

Precontact 50-kHz vocalizations in male rats during acquisition of sexual experience.

50-kHz ultrasonic vocalizations emitted by male rats during a 5-min period before introduction of a female (precontact vocalizations [PVs]) were analyzed in the context of acquisition of sexual experience. Changes in the main copulatory parameters and their N-methyl-D-aspartate (NMDA) receptor dependence, the role of contact with either anestrous or estrous females, and conditioning to odor and background cues were also investigated. Mount latency (ML) and intromission latency (IL) decreased after the 1st copulatory session, but ejaculation latency (EL) changed significantly only starting from the 4th session onward. The number of PVs gradually increased during the first 3–4 sessions. Blocking of NMDA receptors affected PVs and EL but not ML or IL. After a 5-month break in copulatory sessions, ML remained unchanged, whereas EL increased and the number of PVs decreased significantly. PVs were most robustly elevated by contact with estrous females. Exposure to background cues resulted in a linear decrease in number of PVs during 10 subsequent sessions without exposure to a female. The results suggest that, in the course of acquisition of a sexual experience, PVs reflect a learning process that depends on a rewarding value of sociosexual contact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Equivalent Circuits for an SLG Fault Distance Evaluation by Curve Fitting in Compensated Distribution Systems

We present an extended zero-sequence equivalent circuit for compensated medium-voltage systems, with load current contribution accounted for in the zero-sequence voltage drop accounts. It opens its application to complete and eventually filtered waveforms, rather than only one frequency component. Consequently, the new zero-sequence circuit adapts more to fault-location tasks both in overhead and in cable systems, particularly in the presence of important capacitive currents, where extraction of the main charging current may be not an obvious operation. We have applied it in curve-fitting procedures for the evaluation of a single-line-to-ground fault distance. Fault resistance, fault position, and inception angle are fitting parameters. Then, the fault position is given with several percent average error, within a 10% untuning range, at small and large inception angles, and for a fault resistance up to 3 kOmega to be compared to the 50-Omega limit achieved before.     

Low splice loss between 34 /spl mu/m core diameter Bragg fibre and G-652 fibre by using micro-optics

The splice loss at 1.55 /spl mu/m between a 34 /spl mu/m core diameter singlemode photonic bandgap fibre and a G-652 fibre has been dramatically reduced from 2.5 to 0.8 dB by using a micro-optics composed of graded-index and coreless pure silica fibres.     

Electropolishing and passivation of NiTi shape memory alloy

Electropolishing of NiTi alloy has been investigated. The influence of polishing bath composition and the operating conditions instead of the conditions of the process on the quality of the surface, evaluated by AFM and SEM methods, was established. Morphologically uniform surfaces were obtained only in the case of solutions containing hydrofluoric and sulfuric acids. Electropolished samples were sterilized and thermally passivated, then their corrosion resistance was measured in Tyrode's physiological solution. It was established that already after the electropolishing the corrosion resistance of NiTi alloy increases due to the spontaneously formed TiO₂ layer. The increase of the thickness of the layer during sterilization and thermal passivation causes further increase in the corrosion resistance.     

Determination of free surface and gravitational flow of liquid in triangular groove

The solution comprises of two parts. First, for a given groove's basal angle, liquid-solid contact angle, and the Bond number, the shape of free surface is determined starting from the Young-Laplace equation. The optimization technique as developed formerly is applied. Then, having determined the shape of the free surface and slope of the groove, the distribution of fluid flow is determined. The boundary value problem is solved using boundary collocation method in least square sense. Given the distribution of fluid velocity the friction factor as a function of the other parameters of the model is analyzed. Received 25 November 1998     

A modified impulsive force and pressure sensor intended forwaveform reconstruction purposes

The correction of the effect of dispersion on the accuracy of processing in the Hopkinson bar type mechanical transducer enables extension of its application in measurements of impulsive force and pressure of short duration onto the dispersive operating range. In the experimental methods of correction, two-point measurement of the strain inside the bar is usually applied. This way, the dispersive characteristic of the bar is determined and also the process of reconstructing waveforms is performed. In the paper, a sensor of impulsive force and pressure with one-point measurement of the strain inside the bar is presented, in which the incident wave and the first reflected one, generated by the input function, are utilized. Temporal restrictions of the input function and spatial restrictions of mounting strain gauges on the bar, preventing the superposition of the incident and the first reflected pulses in the strain gauges, are given. The nonsuperposition of these pulses is the condition of the sensor functioning correctly. The method of using the sensor for reconstruction of impulsive mechanical quantities, based on the frequency-domain deconvolution, is demonstrated. The advantage of the described sensor is the reduction in the complexity of the amplification circuit and the output signal processing circuit and thus an easier achievement of the required processing accuracy     

Heterologous expression of the Kv3.1 potassium channel eliminates spike broadening and the induction of a depolarizing afterpotential in the peptidergic bag cell neurons

The bag cell neurons of Aplysia are a cluster of cells that control egg laying behavior. After brief synaptic stimulation, they depolarize and fire spontaneously for up to 30 min. During the first few seconds of this afterdischarge, the action potentials of the bag cell neurons undergo pronounced broadening. Single bag cell neurons in culture also show spike broadening in response to repeated depolarizations. This broadening is frequency-dependent and associated with the induction of a depolarizing afterpotential lasting minutes. In some neurons the depolarizing afterpotential is sufficient to trigger spontaneous firing. To test the possibility that spike broadening during stimulation is required to trigger the depolarizing afterpotential, we eliminated frequency-dependent broadening by heterologous expression of the Kv3.1 potassium channel. This channel has rapid activation and deactivation kinetics and no use-dependent inactivation. Expression of Kv3.1 prevented spike broadening and also eliminated the depolarizing afterpotential. Measurements of the integral of calcium current during voltage commands, which simulated the action potentials of the control neurons and those expressing Kv3.1, indicate that spike broadening produces up to a fivefold increase in calcium entry. Manipulations that limit calcium entry during action potentials or chelation of intracellular calcium using BAPTA AM prevented the induction of the depolarizing afterpotential. We conclude that spike broadening is essential for the induction of the depolarizing afterpotential probably by regulating calcium influx and suggest that one of the physiological roles of spike broadening may be to regulate long-term changes in neuronal excitability.     

Nanoscale mechanical properties of polymers irradiated by UV

The application of depth sensing nanoindentation to determine mechanical properties of three different polymers is described in this work using three different techniques to calibrate the measurement system. The nano-hardness and the elastic indentation modulus of polyvinyl chloride, polyethylene oxide and polyacrylic acid were inferred from nanomechanical tests, and the influence of ultraviolet irradiation on the mechanical properties of measured polymers is studied. A multicycling test—a sequence of several loading and unloading procedures—allowed the measurement of changes in the sample viscoelasticity. The nano-hardness of the polymers is shown to increase with radiation dose while the viscoelasticity decreases.